Amazon S3 Plugin for WordPress: “A WordPress plugin allows you to use Amazon’s Simple Storage Service to host your media for your WordPress powered blog.”
Once setup, this plugin transparently integrates with your WordPress blog. File uploads are automatically saved into your Amazon S3 bucket without any extra steps. Once saved, these files will be delivered by Amazon S3, instead of your web host. Any image thumbnails that get created are saved to Amazon S3 too. You’ll also find an “Amazon S3″ tab next to your regular “Upload” tab, which allows you to easily browse and manage files that were not upload via WordPress.